Generally, on a lower portion of a sink table for discharging wastewater, a bathroom, or a urinal for discharging urine, a typical drain trap for trapping a small amount of water is installed to prevent bad odors that emanate from a drainpipe from flowing backward. However, in the case of such a drain trap, the trapped water includes part of the wastewater or urine as described above, and thus, as a result, the bad odors emanate from the trapped wastewater or urine. Further, if the trapped water has been evaporated, the bad odors that flow backward from the drainpipe are unable to be blocked.
As illustrated in FIGS. 1 and 2, a drain device in the related art, which has been developed to solve the above-described problems, includes a trap main body 10 formed to be coupled to an upper end of a drainpipe, a cylindrical container 20 formed to receive wastewater from an upper portion thereof and to discharge the wastewater through a bottom thereof, a closed portion 30 in a bell shape that is connected from a center of the bottom of the cylindrical container; and an elastic container 40 formed in a cylindrical shape and having an upper portion that is coupled to an outer surface of the cylindrical container and a lower portion that is in close contact with an outer surface of the closed portion. Accordingly, if the wastewater or urine flows in through the cylindrical container 20, it is stored inside the closed portion 30 and the elastic container 40, and if a predetermined amount of water is stored, the elastic container 40 is open by the pressure of the water to discharge the stored water downward. After the water is discharged, the elastic container 40 is closed again and becomes in close contact with the outer surface of the closed portion 30 to prevent bad odors from flowing backward.
However, the drain device in the related art as described above has the problem in that the elastic container 40 is closed before the water stored in the elastic container 40 is not completely discharged, and thus a small amount of water that has not yet been discharged always remains. That is, if the pressure of the water that is stored in the elastic container 40 becomes larger than the elastic force of the elastic container 40, the elastic container 40 is open to start the water discharging. During this operation, if the pressure of the water stored in the elastic container 40 becomes smaller than the elastic force of the elastic container, the elastic container is closed again to trap the water. Accordingly, bad odors emanate from the remaining water.
Further, even in the case of discharging the water having small viscosity, such as the wastewater or urine, viscosity acts between the closed portion 30 and the elastic container 40, and foreign objects included in the water stick to outer surfaces and inner surfaces of the closed portion 30 and the elastic container 40. In this case, as illustrated in the drawing, since the outer surface of the closed portion 30 and the inner surface of the elastic container 40 are vertically in surface contact with each other, many foreign objects, which have failed to pass between the surfaces, get stuck more easily. These foreign objects that are stuck between the closed portion 30 and the elastic container 40 widen the gap between the closed portion 30 and the elastic container 40 to cause the bad odors from flowing backward.
On the other hand, since the viscosity of the water has a property of maintaining the closed portion 30 and the elastic container 40 in a closed contact state, the elastic container 40 may not be actually open even by the pressure of the water that is larger than the elasticity of the elastic container 40. Further, if there is no discharge of the water for a long time, the water and the foreign objects, which are present between the closed portion 30 and the elastic container 40, get dried and stuck to each other to block the discharge of the water.
Further, the drain device in the related art is required to be formed of a very flexible material in order to discharge the water and to block the bad odors by the elasticity that acts when the elastic container 40 is open or closed. However, the elastic container made of a flexible material may be lengthened during the repeated opening and closing operation thereof or may be deformed through the reduction of the elasticity of the elastic container due to chemical properties of the wastewater or urine.
Further, in the case where the elastic container 40 of a flexible material has been deformed, the bad odors emanating from the drainpipe directly rises up, and a gap occurs as the elastic container 40 is easily turned inside out or opened by wind that flows backward from the drainpipe to cause the bad odors to flow backward.